1. Field of the Invention
The present invention relates to a washing system for washing a painting truck which carried an object to be painted during painting of the object and, more particularly, to a washing system having a washing apparatus for washing a painting truck conveyed along a truck convey line in accordance with a predetermined route.
2. Description of the Related Art
For example, in an automobile manufacturing line, in order to paint a manufactured automobile body, the body is painted while being placed on a truck (painting truck). More specifically, the painting truck is conveyed along a truck convey line in accordance with a predetermined circulation route. A liquid paint or the like is sprayed by a jet-forming means such as a spray to an automobile body placed on the truck in a painting booth. During painting for applying a paint by a spray to the automobile body placed on the painting truck, the paint is undesirably applied to the painting truck itself.
The paint applied to the painting truck is dried and solidified when the paint applied to the surface of the automobile body is dried. For the next painting cycle, a new automobile body is placed on the painting truck with such a solidified paint. When an automobile body is placed on such a truck or the truck is conveyed along the convey line, the painting truck is vibrated. The vibrations cause formation of a powder of microparticles of the paint attached to and solidified on the painting truck. The powder particles may be separated from the surface of the painting truck and float in the air.
When the paint floats in the form of a powder having microparticles, the paint powder may be mixed as a foreign material in a jet of a liquid paint when the liquid paint is sprayed on an unpainted automobile body placed on the painting truck. As a result, the paint powder is undesirably attached to the surface of the automobile body, and an excellent painted surface (very smooth painted surface) cannot be obtained.
In order to solve the above problem, as described in, e.g., Japanese Patent Laid-Open (Kokai) No. 62-31964, there is proposed a washing apparatus wherein a washing chamber is defined in a route of the truck convey line, and washing water with a high pressure is sprayed to the painting truck conveyed in the washing chamber to remove the paint attached to the surface of the painting truck.
Since a washing solution is sprayed to the upper, lower and side surfaces of the painting truck conveyed in the washing chamber in such a washing apparatus, it includes upper nozzles, lower nozzles, and side nozzles. The upper, lower, and side nozzles are driven by separate drive units. That is, since the upper, front, rear, right, and left surfaces of the painting truck are independently washed, thereby space and cost of washing equipment are undesirably increased.
For example, a robot having a nozzle for spraying washing water may be located at a predetermined position facing the truck convey line. In this case, washing water is sprayed to remove the paint attached to the upper, front, right, and left surfaces of the painting truck while the robot is being actuated. When this method is employed, washing water can be optimally sprayed to one (i.e., front surface) of the surfaces of the painting truck which opposes the robot. However, the surface which does not oppose the robot (i.e., rear surface) may not be properly sprayed with washing water.
In order to solve the above problem, robots each with a spray nozzle may be located at two positions interposing the truck convey line therebetween to remove the paint attached to the upper, front, rear, right, and left surfaces of the painting truck. However, since the two robots each with a nozzle for spraying washing water must be arranged as described above, an increase in cost of washing equipment is left unsolved.